Their campaign, dubbed "Let's Buy a Mountain," was the brainchild of Hall, a land-use attorney and local resident who said he was sick of battling new development after it was already in the works.

Frustration with development has simmered in the Hollywood Hills, where neighborhood groups have complained that the pace of new housing construction and other development has not been matched by the infrastructure to support it. Such complaints were a driving force in the recent City Council election that ushered in City Hall outsider David Ryu to represent a sprawling district that includes Laurel Canyon.

In Laurel Canyon, residents have been worried about losing the rustic feel of the storied, sylvan area known for inspiring poets, artists and musicians like Joni Mitchell. "I always get embroiled in these one-off disputes — this home, that home. It felt very reactionary," Hall said. When he and his neighbors found out that an undeveloped swath of the mountains could be up for grabs, "we wanted to do this a different way."

Instead of battling future plans to develop the hillside, residents decided to band together to raise $1.6 million, the going price for the 17-acre chunk of L.A.'s urban wilderness.

The Laurel Canyon ridge they want to buy stretches between Lookout Mountain Avenue and Stanley Hills Drive, an area dotted with oaks and home to bobcats, coyotes and deer. Environmental advocates say it is a crucial corridor for big mammals in the Hollywood Hills.

"We're watching these incredible green spaces disappear very quickly," said Alison Simard, founder and chair of Citizens for Los Angeles Wildlife. "We need to grab this land where we can and preserve it."

If they succeed in buying the land, it would be turned over to the Mountains Recreation and Conservation Authority, a local government agency that manages open land, to be preserved as green space. The Laurel Canyon Land Trust, a newly formed group, would retain the rights to prevent future development on the mountain, Hall said.

Under an agreement with the current owners, the groups have a year and a half to come up with the money. They must first drum up $50,000 to put down a deposit by early November.

"This is an opportunity that comes once in a lifetime," Councilman Ryu said at the news conference. He urged Angelenos to donate to the cause. "Please donate today so this important piece of L.A.'s green belt will be forever removed from the threat of development."

Simard said the alliance had raised $20,000 as of midday Wednesday. Ryu has also pledged to match up to $15,000 of any additional funds raised to reach that November goal. The money will come from fees charged to area developers that are designated for park funding, according to his office.